1. Field of the Invention
The present invention pertains to a solid oxide fuel cell, and more particularly to a solid oxide fuel cell for reforming a hydrocarbon raw fuel gas and generating electricity using the reformed fuel gas.
2. Description of the Related Art
Solid oxide fuel cells (“SOFC” below) use oxide ion-conductive solid electrolytes; these are fuel cells which operate at comparatively high temperatures, to which electrodes are attached on both sides, and fuel gas is supplied to one side while oxidant gas (air, oxygen, etc.) is supplied to the other.
In conventional solid oxide fuel cells such as that described in Patent Document 1, a box-shaped reformer is disposed at the top of a fuel cell stack; this reformer is heated by the combustion heat produced by the combustion of off-gas flowing out from the top end of each cell in the fuel cell stack. Raw fuel gas and water for steam reforming are supplied to the reformer, and the raw fuel gas is steam reformed by bringing a mixed gas of raw fuel gas and steam into contact with a reforming catalyst filling the reformer.
In a reformer of this type, the raw fuel gas and steam are fed into the reforming catalyst after flowing through a relatively long passageway, so that the supplied raw fuel gas and steam are fully mixed. To ensure that the mixed gas of raw fuel gas and steam fully contacts the reforming catalyst, the mixed gas is reformed as it flows through the relatively long passageway inside the reformer. Patent Document 1: Published Unexamined Patent Application 2010-238600